1. Field of the Invention
This invention relates to an automobile steering device; and more particularly, to power steering with fail-safe torque assistance provided by an electric motor.
2. Description of the Related Art
Conventional electrical power steering devices are often provided with a fail-safe relay in series with the power steering motor. When the motor draws too much current, the relay is opened to stop the flow of electricity to the motor. This type of fail-safe means is referred to in Japanese Patent Laid-Open Publication No. 62-292574.
During the normal operation of this type of power steering system, the relay will be closed. Under certain circumstances the current through the motor may increase so quickly that the relay cannot open fast enough to prevent its contacts from becoming welded together. Once they are welded closed, the contacts cannot be reopened.
Although the welding together of closed relay contacts rarely creates a safety hazard, it is preferable to have such an abnormal event, or fault condition, detected and reported so that the relay may be immediately repaired.